It is known that insulating glass panes need to be sealed so as to be resistant against diffusion of water vapor. For this purpose, a permanently plastic adhesive, which usually is butyl, is applied to both lateral sides of the spacer. In the case of a spacer made of an elastoplastic tape which often consists of several functional layers and is gas-diffusion-tight, a joint is produced inevitably between the “beginning” and the “end” of the tape placed on the one glass pane. Spacers placed or applied mechanically frequently start and end in the region of a corner of the respective glass pane because the mechanical transport processes of the glass pane will be simplified. To ensure that diffusion tightness is also ensured in the area of this so-called corner joint, a film strip made of plastic for example is currently glued onto the corner by hand.